Can't help you with the pansies--never grown them before. But anytime you have tiny
seedlings that are crowded, the best thing to do is take a pair of sewing or toenail scissors and carefully clip out all but the strongest plant. If they are real small like yours, I normally leave two or three in each pot and let them grow a little bigger before I choose the one I plan to keep. Just make sure you have some
growing room between the ones you keep.