Ricky had an assortment of advise typed but I got logged out and lost the reply.
Too lazy and kind of bummed out to type it again but try long sleeves first see if that helps. If it does then (see below)
You can use a cut sock which probably won’t last long or one of those sweat band things or a towel or pot holder maybe to pad it out though till you find out if you’re doing something wrong. The arm sleeve thing keeps you from sticking to your uke or leaving gross arm gunk on your finish in humid or warm weather anyway so it’s useful regardless.