It has to be a red card. No ifs, no buts. Not least because it'll come back to bite you if you ref either of the two teams again, and the same situation occurs but at 0-0 in the 90th minute.
Also, spare a thought for next week's ref who will be trying to apply the laws of the game properly.
Also, spare a thought for next week's ref who will be trying to apply the laws of the game properly.