If it gets more painful, or the redness around it increases, it might mean its infected so head for an all-hours doctor, or hospital, on the weekend. Try to keep it up on a footstool and not walk around on it too much. Your foot looks a bit swollen, not knowing if this is usual for you I'm probably over-reacting.
My god, it looks like a snail has crawled in under your skin. After reading about the grass seed I wonder if one is growing under the skin. I have heard of that happening before. Go to A & E instead of waiting to get into a doctor.
G'day Do you suffer with Gout??? If so could be a gout syst, But anyway get it checked out as you have an infection, the redness round the lump is a dead give away.
Only advice I do not reccomend that you heed my advice except for the fact that you should get it checked out proto.
As it turned out, it was "just" an award winning, Guinness Book of Records attempt, blood blister. caused by localised irritation (Doctor speak) from a grass seed lodged in my sandals. According to the Doc there are few nerve ending in that part of the foot, so you wont feel it happen.
Probably would not have happened if i had bought some of my usual plastic and rubber sandals from Kmart, but they were out of stock.
I felt sorry for the pretty young sales assistant at Athletes Foot and paid $178 for genuine leather and suede sandals instead, later found them on the internet for $70.......
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Cheers, Chris...
"The problem with doing nothing is not knowing when you're finished" - Benjamin Franklin