You should be fine. As long as you go to a reputable artist, first off. The main thing you need to make sure you concentrate on is the aftercare. Ignore those people telling you that savlon or other things are great, Savlon contains a scabbing agent, which is bad for your tattoos. As someone above mentioned, Bepanthum is the best thing to use. You only need a small amount onto the tattoo, three times a day. Keep it clean at all times. With it being on your foot, the blood flow is slower, as it's further from the heart. I have a calf sleeve, and it was started before I was diabetic (type 2 ) then when I added more, after being diagnosed, it got infected. It's all good now, but this was a massive piece I had done, whereas yours is only small, and should be fine if you look after it.
Any tattoo can get infected, or take a while to heal, regardless if you're diabetic or not. It's all down to the way you look after it once it's done. Whenever I got red ink on my skin, it got infected and reacted to it. Now my diabetes is under control, I have no problem with red ink. My thigh length Spider-man tattoo can couch for that!
