My son accidentally hit my two year old daughter with a cricket bat on her mouth and nose, what should I look out for and should I let her sleep

How long before you wrote this question? She should be crying and fussing for quite a while before wanting to sleep. Wanting to sleep can be a sign of concussion or other serious problems. Although the blow wasn't to her skull, so concussion is unlikely... Call her pediatrician.

Of course she can be allowed to sleep, regardless.

Teeth can get gas in them after a blow, but since she has baby teeth, I wouldn't worry about her teeth. At some point wiggle them gently.
A broken nose is cartilage than can heal easily enough.
An Xray might be ordered of the bones of the jaw and cheeks.
All in all, odds are she is OK, but let her doctor decide. Leave a message because it's Saturday. Only you know how hard he hit her, so you decide about going to an ER.

You take her to the ER now. Not later. Run, don't walk.

I defer to J_9

You take her to the ER now. Not later. Run, don't walk.
Z
Yes, totally agree. Why did she waste time asking here and wait for an answer !

You look out for traffic as you drive her to the ER.

Maybe, just maybe, it wasn't much of a hit at all!
I got through my entire childhood with far worse. I was hit full force with a golf club, in the temple. ETC!
I try to at least provide some info, with disclaimers. Not everyone is anywhere near medical care, nor has a car, nor can afford an ambulance, and so on. She could be in an ER waiting room for 8 hours, catching diseases from others. I've been in ERs that were longer waits than 8 hours, and care was lousy. Was there blood from a blow to the mouth? There should be, to merit that amount of concern. I at least tried to find out how long it's been.

Maybe, just maybe, it wasn't much of a hit at all!
I got through my entire childhood with far worse. I was hit full force with a golf club, in the temple. ETC!
I try to at least provide some info, with disclaimers. Not everyone is anywhere near medical care, nor has a car, nor can afford an ambulance, and so on. She could be in an ER waiting room for 8 hours, catching diseases from others. I've been in ERs that were longer waits than 8 hours, and care was lousy. Was there blood from a blow to the mouth? There should be, to merit that amount of concern. I at least tried to find out how long it's been.
Stop apologizing. It is a toddler. No one fools with an accident like this in one so young.

Stop apologizing? I never started. Far from it.
No one? Plenty do. My mother did. Again - we have no idea how serious it was. I won't sit here all day telling everyone in the world to get to an ER.