No, the cut does not place him at risk either.
Moderate is between high and low. If I were your mate, I would not worry. EWH
What about the cut on his finger? Can that be exposed to HIV and STD?
When you say moderate, meaning?
Welcome to the Forum. While your mate's actions placed him at some risk, the risk is, at most, moderate. Most commercial sex workers do not have STDs or HIV. EVen more importantly, oral sex is an inefficient way to acquire STDs. Of the bacterial STDs only gonorrhea is acquired through oral sex; neither HIV or chlamydia is and without an obvious sore or lesion on your partner’s partner, the chances of syphilis and herpes is likewise tiny. If he had gotten gonorrhea the infection woul most likely be asymptomatic. Even if his partner had an STD (any STD and it is likely she did not), most exposures do not lead to infection. He can have his throat tested for gonorrhea to rule out that possiblity.
I hope this comment is helpful. EWH