I Feel A Lump Deep Under Skin On Left Buttcheek.

I feel a lump deep under skin on left buttcheek. It seems to move around and as if I chase it trying to rub it. When I do get to rub it is send shooting pains thru my thigh and knee. About 6 months ago I fractured my hip on the same side and have multiple fractures thru my L3 L4 vertabre. And a piece of my spine is completely broke off.