I noticed today that the is a small hole in one of my cacti. I checked the roots and they are fine, no rot or anything and they seem very healthy. I'm pretty sure I'm not over watering, but I could be under watering. I also noticed that the creases in the cactus have gotten a lot deeper and that it is starting to grow sideways. I'm not sure if it is trying to grow towards direct sun or what. It is still very firm and healthy other than the hole from what I can tell.

Can someone help me help this poor guy out? I'll be transferring him into a gritty mix sometime this week, so I knew the soil isn't the greatest.
Thanks in advance-Sam ðÂÂÂðµ