leaking from new faucet supply line

I just replaced my bathroom vanity valves and supply lines, along with the faucet. All working, but I have a slow, gradual beading of water on the cold supply line, right above where the hose joins to the nut (see attached). It occasionally drips off, but very slow. This supply hose attaches to the valve with a small rubber gasket inside of it. Do I need to tighten the nut harder? It's already pretty tight - is it possible I over tightened and damaged something? Sorry if these are dumb questions, but I'm a beginner at all of this.

Thank you

Over-tightening can damage the seal in the hose.

It is pretty hard to damage it by overtightening, but one problem is the valve. if it is a new one, which it appears to be. It would have been better if it were a 3/8" compression for the hose instead of 1/2" ips. All you can do it tighten it further and see if that stops the leak.