Forearm tightness and pain. Limited in the motion of supinated biceps curl.

Maybe try a lighter weight. I don’t think it’s really necessary to go heavy on curls or at least to rush the progress. Take the reps slow and make sure you’re doing them correctly and not swinging your arms just to get the weight up. Or maybe try doing them with a hammer grip.

Tightness and soreness not uncommon - some could be form, some could just be the muscles are still weak relatively (those are small muscles doing a good bit of work on curls). Pain could just be from overstraining, but that's harder to brush over.

Small fix for forearm help during curls, make sure your grip is loose at the extension of the movement and you don't squeeze til you get past 90* at the hinge. Alot of people keep their grip squeezed tight throughout and that can put a lot of extra strain on the forearms.