Forward progress on goal line

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I had a call last week (I'm LJ). A is on the 1 yard line, first and goal. Running play off tackle to my side. Runner is hit and stopped short of the goal. Here's where it gets tricky. He was met by 2-3 defenders. They stopped him, but they did not drive him back. He was not down nor was there any assistance from his teammates (A). There was no whistle. He was "wrapped up" for about a second, at which point he started to spin out of the tackle. He crosses the goal line and I can a TD.

From the time first contact was made by "B" until he crossed the goal line, was no more 2 seconds.

You can imagine the "B" coach was irrate the forward progess had been stopped. So if your working the line how do you judge when to and when not to stop the play?

I am not second guessing my call (had the "A" player spun out of the tackle and then fumbled, I wouldn't have stopped it over forward progress) I just wanted to know if anyone with more experience can help a relative newbie out on this judgement call.

Jim