Get it checked by your practice skin specialist GP, or referred if you don't have one. They will need to look at it with a lens to see the types of cells in it to classify it.
I'll doubt if it's diabetic related.
Looks like you've been squeezing a whitehead or it could be an insect bite.
Check it out with your gp if you're concerned.
Doesn't look like anything to worry about though.