My tattooist hates working on people who've used numbing cream as it makes it harder for him to tattoo the skin and can badly affect the healing. Best to take ome painkillers beforehand if u really have to and have plenty of breaks. Feet don't always heal well so personally I wouldn't do anything that might make the healing worse.

Don't forget though that painkillers thin the blood and too much bleeding can affect the healing.

Good luck