What Causes An Open Sore On The Chin Of An Infant?

Hi... think I need pediatric/ dermatologist assistance. My granddaughter developed a red raised dot on her chin 2 days after her 1 year birthday... while fighting a daycare cold brought home by her brother & sister. The next day it was an open sore about 1.5 cm in diameter-located exactly where her hand contacts the chin while sucking her finger. The following day it was larger, less than a dime in size. The daycare has hand, foot,& mouth going around... and it was thought maybe her subs brought it bine to her. The next day... no larger and looked drier. Today it dies not look better & there is another spot on her cheek & maybe a tiny one on her chin. They have just moved to this state in the last 2 weeks and have no healthcare. Is there a way to attach photos to show you? It is impossible to keep anything on that location... but we have tried, using antibiotic then antifungal creams