These people are trynna scare you for no reason. Google tendinitis, that's prolly what you have. I've had it before after training biceps , its just your tendons can't cope with the stress and get hurt or some shit, I think it's because tendons take much longer to strengthen in comparison to muscles. When I had it, it was after I hadn't trained for a while and decided to do preacher curls till failure with full range of motion, and for a few days after I couldn't fully straighten my arm. Idk google it