Boyfriend has blister on big toe. it is really big. warm to touch. it hurts but not much. he has diabetes buy it's under control. diabetic neuropathy?

Probably not: Neuropathy, diabetic or otherwise, is a condition whose hallmark symptom is decreased sensation especially to pain. In an advanced diabetic, especially with poor control, a blister on the toe could be a serious condition and the seminal event for a diabetic foot ulcer. Do not ignore this especially if it doesn't heal in 2 or 3 days.