The top of my foot keeps hurting.

I'm not sure if it's because I've gained weight, but I suddenly experience pain on the top of my foot whenever I walk.

When I sit again and start walking, the pain comes back and I walk with a bit of a limp.

If you walk or run quickly, it gets worse, and generally, sometimes it hurts when you walk, and sometimes the pain is less.

How should this be treated?