Hi There, I've Noticed In The Past Week A Hard

Hi there, I've noticed in the past week a hard painful lump just to the side and down a bit from my hip bone. It doesn't move when I try. Really quite worried about it being a form of cancer? I'm hoping to get the my GP this week but they're always fully booked so I'll probably have to wait 2-3 weeks to see my Dr. Any advice and information would be great please!