What Does A Lump On The Waist Indicate?

Hello.

I have a near golf ball size lump on my waist line on the left size. It's been there for two months now but was previously the size of a pea and has suddenly gotten bigger. It's slightly red now and only moderately painful. I'm a 31 year old male with Crohn's and on humira. I saw an emergency room doctor while it was still small and he thought it was maybe a lipoma but wasn't sure. The fact that it's now getting much bigger has me concerned.

Thanks for any help!