I would say no, I remember potions only being allowed in combat, and only one per round. The good news is, you can decide to use it after a roll. So if you have a +2 Speed potion, and you lose the speed roll by 1, you can then take your potion and win the round. Same with the Brawn potion, which is great if your attack leaves your foe with 1-2 hit points. But if you’re trying a skill challenge, rolling one or two dice and adding your skill to try to top a number, the potion may give you too big an advantage. But it’s your book, and if you feel using a potion on a skill roll makes sense, go for it.