It is unsafe for us to diagnose any kind of medical condition over the internet, even if we have pictures. I know the veins of the feet can seem like great spots to inject, but these veins are actually quite fragile and are not as great as they may initially appear. Injections into these veins end in extravasation to a much higher degree than injections in say the cubital or basilic veins of the arms.
Now, we need to consider the fact that Cocaine is highly caustic to surrounding tissue. This numbing effect as a result of restricted blood flow to the area is part of what made Cocaine so popular in the medical community to begin with.
If the site is still painful and/or uncomfortable, red and warm to the touch, you most certainly should have a doctor check it out as it could likely be an abscess in the making. The longer you wait to have it checked out is going to dictate proportionately the time it will take to treat and recover. If you catch it early, it can be handled pretty easily, even potentially by your PCP. If it is caught later, it can entail full-on surgery with anesthesia and everything.
TL;DR You should definitely go to the ER and have them figure things out for you.