Blister on baby's finger

I noticed this on my daughters finger today and when I showed my mom she thought it could be chicken pox but said they usually start on the torso and work their way out. My daughter has been playing in the playground a lot which has wood chips on the ground so I'm thinking it's a splinter that got infected. Any ideas of what it could be and what I can do to treat it? I should also add that it is not bothering her at all.