sorry for you but can you not say that
can't you just say that somewhere else

I was doing a story with my friends (by drawing) and I drew a boy like it a funny romantic story, when they saw the boy giving a flower to my friend's character they called me gay

Man, sorry for you

Uh....It happens... but try to forget about it.. and try to get your friends to talk to you again and tell them that what you did in class they should forget.
We all make mistakes, your friends will soon be understood. :)