Heating element in oven not working - can I still use it?
I think the oven is probably safe electrically, but you should immediately have it repaired. You could "throw parts at the problem" by just replacing the heating element yourself and this might fix it, but it could be something else.

You could remove the element and test its resistance. When our oven went I out I decided to first test the temperature sensor (thermistor). I spent a lot of time on this and the tests indicated it was OK, but testing a heating element might be simpler.

How old is the oven? Is this a stand-alone oven or is it in a stove?

The oven in our GE 30" base quality (but self cleaning) electric range was first erratic and then would not heat. It turned out to be the controller/display module (aka the "oven timer"). The range was over 20 years old and I could not get a new timer module.

I ended up removing and sending the timer to a company (in Ontario, Canada) which repairs them and within a week or 10 days got it back (total charge was about $125). That was 7 years ago and it has worked perfectly since.