Possible overwatering. How to revive?

Hi all. Thia ia my first grow and I am doing it outdoors as I live in spain (near Alicante). I think I overwatered one of my plants (stupidly I my excitement to get them planted I never noticed there wasn't any drain holes in the pots, watered had seeped from the bott so i guess there is a crack in the pot somewhere) I have read different things about leaving them to dry out or re-pot. What is the best way forward to try and re-vive my plant? Any help will be much appreciated.

Here is a picture of the plant.

Put some drain holes and let the soil dry out.

Thanks I have done that and it is already looking better