Oops - sorry. I mistook the age you gave for his age, not hers.
Aj
He should indeed get some testing done to confirm this. This isn't sounding like hsv1, as he probably wouldn't get it on his hands - that's very rare - nor would he get it on the roof of his mouth, most likely.
And not to sound rude, but this is up to your daughter. There isn't anything you can do, and shouldn't be doing, if she's an adult, and I am assuming she is, or she wouldn't be dating a 23 year old for 4 years.
She should also be tested for herpes, and should ask for a type specific IgG blood test. Over half of adults in the US have hsv1, and only 20-40% of those will ever get a cold sore. If she has hsv1 antibodies, and that's indeed what he has, she can't get it again.
And if she gets it, she gets it. By the time we are elderly, about 80-90% of us will have it anyway.
If he doesn't have insurance, he should call the local health dept and ask what services they have for people who have no insurance so he can get further evaluation.
Aj