Getting a cast iron skillet surface smooth
You cannot expect to ever have cast iron perfectly smooth. Its surface is uneven due to the manufacturing process, what producers like to call "pebbly" in marketing materials. 

The pan in your picture has not taken the seasoning in the best possible way, it could have been smoother without the thicker parts. But these are not the dreaded "flakes" of failing seasoning, just buildups which are strongly bound to the pan. 

If you insist on perfection, you could strip the pan and reseason it from the beginning, but it's lots of work, and there is no guarantee that your second try will work better than the first, you typically need to go through more seasonings before you get a feel for the craft. I'd say use it as it is, there are no noticeable downsides in the prepared food.