Nexus 5 stuck on "flying color dots lollipop" screen after Hard Factory Reset I just did a wipe data/factory reset on my Nexus 5. I followed this YouTube tutorial.

I'm stuck on the boot screen, which was my problem in the first place, and it's been on the boot screen for 25 minutes. 

Should I wait or do something else?
If you have been waiting an excessive amount of time for your phone to boot (eg. leaving it overnight to boot) but it is still at the boot animation, you may be in bootloop. This is when the phone fails to boot due to some errors in the /system partition. As a preliminary measurement, you should perform a factory reset (or wipe /data) to see if that helps. If  that does not help, you should reinstall the /system partition.


First, you have to format your /system directory; you will need a custom recovery to do this. I recommend TWRP (Nexus 5), but regardless of which recovery you choose, you should download the latest version.
Power off your Nexus 5, then press and hold Vol-, Vol+ and Power simultaneously. Don’t release the buttons until Fastboot Mode menu appears. Excessive force is not necessary and may break your buttons.
Now, you will have to use the adb and fastboot tools. Open a terminal/cmd in your adb/fastboot folder on your PC. If you have the Android SDK, they are usually located in /path-to-sdk/sdk/platform-tools/. Alternatively, you can install the Minimal ADB and Fastboot tool for Windows (or sudo apt-get install android-tools-adb android-tools-fastboot for Linux).
Now plug in your phone to your PC. Making sure that your phone is in fastboot mode , type into terminal/cmd: fastboot devices to make sure that your phone is properly connected (it should return a serial code to you). This next command will perform a factory reset on your phone, so be wary that this will wipe all user data from the phone: fastboot oem unlock. After you have issued that command, type fastboot reboot. You will be presented with a screen containing an android logo and a progress bar (this may take up to ten minutes to complete). After that, your phone will try to boot up again. Just power it off after the android logo and progress bar are no longer on your screen.
Now we will use that recovery.img file we downloaded earlier. Reboot your phone into fastboot mode with Vol-, Vol+, and power, as in step 2. Make sure it is connected with fastboot devices. In the same terminal/cmd, type fastboot flash recovery /downloads/recovery.img, replacing /downloads/recovery.img with the full path to your downloaded recovery.
After that is done, on the phone, use the volume buttons to scroll onto "Restart Bootloader" and hit power to select it. After the bootloader reloads, use the volume buttons to scroll onto "Recovery Mode" and power to select it. You should then be greeted with your newly installed custom recovery.
These are instructions for TWRP: Once your recovery is running, tap Wipe > Advanced Wipe and tick only system, data, cache, and dalvik cache. Now swipe to Wipe. This will wipe all system and user data from the device; data on external sd cards will be preserved if you only selected those 4 partitions.
Now, you will download a fresh system image. If you want to stick with a stock ROM, here is one from XDA (This version is rooted). There are many custom ROMs available on the XDA thread. Download the ROM image.
Now, back in TWRP, make sure you are on the home screen (there should be a home button on the bottom) and go to Advanced > ADB Sideload then swipe to activate the mode. Type adb devices to make sure your device is properly connected, then type adb sideload /downloads/ROM.zip, replacing /downloads/ROM.zip with the full path to the ROM (.zip file) you just downloaded. This may take up to ten minutes to complete.
After that is done, just reboot! From the TWRP home screen, go to Reboot > System and it should boot correctly. Keep in mind that the first boot may take up to an hour to complete, so keep it connected to a power source!