Need help figuring out what is wrong with this beauty. Thanks!!

[Marzhattan]

I got this little guy on the fly in a store and brought him home but have absolutely fallen in love with him since then. I know nothing about caring for him and have been taking crash courses through google lol. Hoping you guys clue me into whether I'm doing something terribly wrong the spots have me worried as well as the scarring he was absolutely green when I first got him so I know it was my fault.
Im not over watering also he is in the sun I live in NYC so all the sun he gets is from behind a windowsill. Thanks I've posted on reddit but have gotten mixed replies. Crossing my fingers for some advice.

[esp_imaging]

The white patch in the 2nd photo is the most worrying. It's possibly that the plant split due to a sudden growth spurt from (over?) watering.
I'd poke around gently in there with a wooden stirrer or something - it looks a bit like you have a big nest of mealy bugs. If so, swabbing them with a cotton bud liberally dipped in alcohol should sort them out, watch carefully to see if they have any buddies elsewhere on the plants.

The other scars don't look like a problem - they look like healed-up physical damage (being scraped, scratched etc during transport or handling), not an ongoing disease or pest issue.
The lines of dots are probably puncture wounds from another cactus. They may have happened before you bought the plant, the scarring is often most noticeable a while after it was damaged when it is fully healed over.

[Marzhattan]

Thank you so much for your response!