Rules of Golf - unconceded putt in match play
Rules
You can’t tap in an unconceded putt in match play

If you knock your ball to two and a half feet and your opponent now lies further away but doesn’t concede your putt, you can’t go ahead and tap it in in match play as you would be able to in stroke play.

While there is no penalty, you could just be asked to replay the stroke in the correct order by your opponent under Rule 6.4a (especially if you went ahead and holed it!) you may feel aggrieved, but you shouldn’t do as the order, and the change in the psychological dynamics that come with it, are important elements of match play- three-footers are harder when you have to make them to save a half or win a hole!