It can be dangerous, especially if it's MRSA. My MIL was hospitalized for 10 days on IV antibiotics for cellulitis that was resistent to most antibiotics.
Hope he responds quickly to the antibiotics.
I had that once in my thumb and it traveled up my arm in 24 hours, 7 days on anti-B's IV's plus again at home after the insurance company kicked me out of the hospital. Another day later, would have hit my organs. Very serious infection, takes months to recover from it.