If you want to study more, you could use the self-study script? It won’t count in your SRS, but you can make sure stuff is well and truly in your short-term memory and keep yourself busy for another few minutes if you want.
After you’ve done that, though, I really recommend leaving stuff alone and letting your brain rest.
I remember when I started I was worried I wouldn’t be able to build up enough of a habit if reviews ended so quickly with little to do afterwards. “How am I going to remember to come back?” It was just over too soon. I can assure you that this problem is far more rare as you start hitting level ten and beyond—lessons come and go but reviews are just about eternal.
Try to remember that you can always practice what you’ve just learned in a different way. You could practice writing the kanji you just learned, for instance, write short sentences with them, or build mnemonics for the ones you feel like you might forget soon. You could check out bunpro or kaniwani. Or you could set a timer on your phone to remind you when your next reviews are coming in, so you have a prompt to log back in when there is more to do and you don’t have to worry about it in the interim. These activities are totally up to you.