There is a skill reset item that you can buy from the cash shop but that requires real money or someone to gift you one (you can pay him in in-game gold or it can be free)
Otherwise, you gotta restart your char. If its only oone point, I suggest you dont restart unless your only like lvl 20 :P
If your in the 40s, then it'd be a pain to restart just for one point, unless your a perfectionist