Touching a mark costs a One-Turn Penalty (rule 44.2) unless the sailing instructions say otherwise. The marks that count are the starting marks before you start, any mark that begins, bounds or ends your current leg, and the finishing marks after you finish (while you are still racing). An inflatable from a different course, or a mark from a previous leg, does not count.
If you were forced onto the mark by a boat that broke a rule, you are exonerated (rule 43.1). If you hit the mark while sailing within mark-room you were owed, and the other boat's failure caused it, you are exonerated too.