The 21-year-old came off the bench to score the winning goal for his side in a 3-2 success over West Ham United in the Premier League.
The result means Newcastle have some breathing space between themselves and the relegation positions as the season goes into its final stretch.
Arsenal would ask for roughly £20 million to sell Willock, who has scored three crucial goals for the team so far during his loan spell.
Speaking after the win over West Ham on Sunday, in which Willock scored the winning goal, Bruce admitted he would love to keep the Englishman.
"We'd love to keep him here," Bruce said. "He is the type of player you want to build your club around. Whether that is possible I am not so sure.
"He won't want to be a super sub. As a young player I thought he had a really good impact. You dip them in and out. He is only 21 and a hell of a player and a great lad.
"He had a really good start and scored on his debut. He now has three goals and vitally important ones. The reason why we brought him was his ability to get forward and score.
"He is disappointed he didn't start. He was in my thoughts because he'd trained so well. I did feel he'd dropped off a little bit, but he is a young lad and that happens. So we are delighted he got the winner for us."