expression, suru verb (irregular)
leave it at that; let it be; stop there
Used to suggest stopping an action or discussion at a reasonable point, often as a request or imperative (e.g., その辺にしとけ). Implies 'that's enough' or 'let's not go further'.
もう遅いし、今日はその辺にしよう。
It's late, so let's leave it at that for today.
冗談はその辺にしとけ。
That's enough of your jokes.
Phrase combining その (that) + 辺 (vicinity, approximate point) + にする (to decide on). Literally 'to decide on that vicinity', idiomatically meaning to stop at a reasonable point.