The goal which settled this tough encounter was the Bermudan international's 19th of the season and his sixth in five matches between the teams, but Parkinson warned Bradford's leading scorer he would have to continue to play well to keep his place in the side.
It was Wells' first goal since Bradford's 2-2 draw at Fleetwood at the beginning of February and his manager said: "Nahki is looking sharp again.
"He has got his rewards for training well and a couple of good performances, but he has got to make sure he continues to produce his form because we have got players on bench chomping at the bit."
The result lifted Bradford to eighth place, two points off the play-offs with a match in hand after losing only one of 10 matches since they were beaten 5-0 by Swansea in the Capital One League Cup final.
Parkinson added: "Northampton are a very good side and we knew what they were going to do.
"We knew we had to be very strong and physical against them, but we also knew we had the quality to create opportunities. It was a high energy game and we were brave with their set pieces while trying to hit them on the counter attack.
"We should have scored a second goal and had some great chances to kill off the game, but we got the important goal and that was crucial for us.
"When you play against Northampton the two centre halves and the keeper are very important. We gave Andrew Davies the job of attacking the first ball and he was immense.
"There is a belief growing in the team, players are coming back into form and you can feel this in the dressing room. I don't think there are too many teams (who) can live with us physically in this division."