This is the star Alnitak, the classic astrophotography killer in the Horsehead Nebula. Also combined with the well-known microlensig effect of ASI 1600 on very bright stars.
There is not much to do, but you could try first removing the stars and then do some tedious retouching work, preferably in PS which is superior for this.
As soon as I saw the image, I knew it was taken with an ASI1600MM. I spent hours trying to deal with the same lensing effect.
https://astrob.in/gsowrm/0/
Finally, a friend explained that there isn’t much to do about it other that touching up the area. I did that, but felt like I was cheating. Haha. I wasn’t able to reshape Alnitak to a circle, so I just smudge some of the spikes radiating out, and left the big ones at N, S, E & W positions.
Before I did this, mine looked exactly like the one in the OP.
Anyway, I posted so I can follow, hoping someone gives you the answer. I spent a lot of time collecting that data. I’d like a better final image.