When my wife gives me a blowjob she likes to bite. While it can be painful I tolerate it, and it seems to excite her when she gets a reaction. At first I asked her to go a bit more gently but she shrugged it off saying pain and sex can go together.
The good news is she lets me finish on her face or in her mouth. She doesn’t swallow it at once, she swills it around in her mouth and shows me first, like she’s seen it on some porn vid. She said this is the best bit. She likes getting some off her face and licking it. It’s fun but sometimes she can bite too hard.