Nursing strike

My 9 month old has gone on somewhat of a nursing strike the last week. He’ll nurse first thing in the morning except one morning but I can’t get him to nurse again. If I do get him to nurse at all it’s only a few minutes and only on the right side. Yesterday he wouldn’t nurse or take a bottle while we were out. I’m going to keep pumping this week and trying to get him to nurse but if he doesn’t would nursing him once a day do him any good or should I just completely swap to formula? I don’t pump enough milk to exclusively pump.