I had some tenderness on the ball of my left foot so I thought it was a muscle pull but then after a few days…

I had some tenderness on the ball of my left foot so I thought it was a muscle pull but then after a few days I was starting to think that maybe I had stepped on something even though I don't remember any painful incident like stepping on a bee or piece of glass. I have been walking barefoot for about 15 years (which has been very good for my foot health and overall health) although mostly on grass/sand/dirt in the warmer months and inside my house year round but I did walk on a rougher prairie area shortly before this started. I see a tiny slit on the bottom of my foot but the more tender part is actually directly above that below the 4th toe and there is also a small dense raised up area (see photo). It doesn't hurt, just some mild discomfort when I put pressure on it, but I am concerned since the rest of my foot and ankle started to swell up about a week later (see photo comparing feet/ankles) and became kind of red. There is no pus or red streaks or fever. A friend was able to get a better look and said he didn't see anything and actually thought it was sprained. It is possible that by walking on my heel to avoid putting pressure on the ball I made it worse and caused more swelling, hard to say. I have been soaking it in salt, putting neosporin and baking soda paste on it and elevating it a few times a day. I also put some moleskin on either side of the tender part so there is less pressure on it when I walk but I only started doing all of these things about a week afterwards, so just the past 2 days. Any other suggestions? Or should I get a blood test to see if it's infected? I am not in pain and it is such a small spot but I am concerned it could escalate but I don't really know what exactly is wrong.