With the game level in the second half after Hibs striker Eoin Doyle had cancelled out Paul Heffernan's opener, the former Partick Thistle player was shown a yellow card by referee Bobby Madden after going down in the box when challenged by Nelson, the caution taking him over the disciplinary threshold which brings a one-game ban.
Nelson denied admitting it was a certain penalty but said: "There was contact but how far down he was when the contact was made, I don't know, we will have to see it again.
"As he slipped the ball to the side he was already going down. It could have gone either way but the referee saw it so I am not going to argue.
"But it is probably doubly harsh that the lad got booked as well. Just because the referee doesn't think it was a penalty doesn't automatically make it a dive so I think it is harsh when it happens to people.
"It might lead to the lad getting a suspension further down the line so he probably feels hard done by and we wouldn't feel too happy if that happened to us.
"But by all accounts there was a penalty (for us) in the first half when (Mahamadou) Sissoko was pulled back at a corner."