Likely just gassing out. Don't worry. Warmer temp=gas coming out of solution.
Beer in a fermenter will make the airlock bubble after fermentation is done for various reasons. Move the fermenter and bang, it will bubble a bit for a while. Dry hop it, same thing. Warm it up, same thing. I notice beers that are totally done fermenting for longer than a month sometimes letting a bubble out here and there. Ambient temp fluctuates, etc etc etc.
As they say, relax etc...
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