[Help] A competitor keep rating 1 star for my app

I have been working on my app for several months and now the app is getting a little popular.
But now a competitor who has much more users and reviews than mine starts to give 1 stars. (>99% sure that it’s them from such evidence)
I think they felt pressure seeing my app becomes popular gradually. It’s a pity that they did that, but I have no good idea to deal with that.
Thanks to their 1-stars ,now my rating in play store drops from 4.8 to 4.6 …

Please, could experts here advice a way to tackle it?

Thank you very much for your answers!