I got a splinter or something in my foot about 4 months ago, and it's been a little painful to walk barefoot during that time. it also hurts with any pressure applied to the small area, and it is a small visible bump/lump right there, slightly brown color

Splinter: If it still gives you pain would go to a dermatologist/surgeon ( since it is 4 months and epithealized ) to have it removed( they usually come out on their own) ,also have them check out the brown coloration, that it is not a mass. f/u with dermatologist /surgeon..

End the Problem.: A talented surgeon should have no difficulty extracting the foreign body, or what's left of it, along with dealing with the inflammatory tissue. Probably best performed under an out-patient setting but in-office could be possible.