What Causes A Painful Hard Lump On The Ulna?

I have a hard bump on my ulna between my wrist and my elbow. It hurts whenever there s even the lightest touch on it. It s been hurting for about 2 months now. I thought it would get better, so I started lifting again, and now I m in extreme pain. I was doing bicep curls and it just felt like a knife was stabbing my arm. What could it be and should I be worried?