Slightly painful, hard lump on the bottom of my foot near the heel?

It’s almost on the back of my foot, but still on my heel if that makes any sense. It’s slightly painful and hard if you feel it. It’s under the skin though so if you would just look at it without feeling it doesn’t look like there’s anything wrong at all. I tried googling it, but nothing really sounds like what I have. Most people have something on the outside of their foot too not just under the skin. Any ideas as to what it could be? I found lately that since I’ve been wearing these one pair of shoes that are wearing out my feet have started to hurt in some areas. I’m guessing it’s the shoes? But what about the lump!?