Risks with phimosis
There are 2 risks with phimosis when leaving phimosis untreated, and that is Paraphimosis and hygiene issues. Paraphimosis is the state of penis when foreskin is behind the glans and is unable to slide back to the tip of glans. This can require medical supervision. While hygiene is hygiene, you can risk fungal infection and a few others if hygiene is not maintained.
Note
You will get better sex sensations if you can retract your foreskin but it's not a big deal if you don't, especially if you're already fine with your current state.