I had a 5 lb pale once that I left unrefridgerated for months and it had molds and funky stuff on the surface of it when I opened it. I froze it and it never got completely hard. I cut the top of the pale off, sliced off the funky surface, got the partially frozen chunk all the way out of the pale, rinsed it on all surfaces just for a moment, and then threw it in my boil and made a DELICIOUS brown ale with it. You'll be a-ok.