。
Stop fiddling with your hat.
Literal
Hat [object-を] fiddle-around [nominalizer-の] [topic-は] stop-[soft-command-なさい]
Note the structure [verb plain] + の + は + [another verb] — the nominalizer の turns the first clause into a noun phrase, then は topicalizes it so the second verb can comment on it. Literally 'as for the fiddling-with-your-hat, stop it.' 弄り回す is a compound verb: 弄る (fiddle with) + 回す (turn around), intensifying to 'fiddle around with repeatedly'.