I'd suggest just wait through this and do some cardio from time to time. I have noticed quite a shrinkage in my lower arms, but my biceps circumference is exactly the same as it was ~30 cm. Yet, when I flex it, barely anything happens, so I suppose it has partially melted into fat or smth, but now I need to either starve myself or do lots of cardio - which is tricky in winter and I cant go to gym/pool anymore 🙁 - to burn that excess fat down. Btw, my best female friend is doing a lot of jogging, pilates and such as, and she has bigger upper arms than I do - and she looks in a very good shape for someone who is 40 years old.