If it was my cat.... and the wound is not actively bleeding, cat is acting normally otherwise, not shaking the head or pawing at the ears, not keeping ear folded like it hurts or crying like it hurts.... I wouldn't take them in to work with me if that helps any.

Although I have the priveledge of just asking one of the vets at work about it and they either tell me to clean things with peroxide or put Panalog cream on it, depending on what the wound is. If they think it needs looking at they tell me and I bring in the cat.

You should be able to just call Lily's vet and ask if they think this needs to be looked at or if they can recommend what to clean it with and just watch for complications.

Ears are a fragile thing so it could have been a fight, or just really rough playing, or dashing through the house not looking where she was going.

Poor Lily. Whatever happened I hope it doesn't happen again and this heals up quickly with no problems.