The 11-year-old gelding missed running at Warwick on 15 January because of a muscle problem in his back which was spotted when he was being ridden out. O'Neill told BBC Gloucestershire: "It was only a minor one, he's fine again.
"We didn't think he was quite right last week so we got the back man to him, he tweaked him up and he seems fine again - so onwards and upwards."
Don't Push It carried 11st 5lb when winning last year's Grand National and is likely to carry more this time round.
To avoid adding to that burden both of his races so far this season have been in hurdles at Cheltenham where he was pulled up in December and finished 12th out of 17 on New Year's Day.
Despite missing out on running at Warwick, O'Neill is keen to get at least one, preferably two more runs into Don't Push It.
"It's just finding the right races for him at the right time when he's right," he said.
"I'd like to get him in to winning ways before we go back [to Aintree] so it'd be nice to try and win a race with him.
"If we can get another couple of runs into him he might be able to pick one of them up and back to Aintree here we come."
O'Neill also confirmed Can't Buy Time and Welsh Grand National winner Synchronised are also entered for Aintree.