I Have Two Ulcers On My Buttocks. One On The

I have two ulcers on my buttocks. One on the right one on the left. My in home nurse comes every other day to change the dressing. I noticed tonight that i have a lump in the left side that's about 1/2" long going from the ulcer towards the anal. It's hard to sit or lay down. What would cause this and should i be worried?