my older cats interactions with younger cat

so i have a cat, suki (3m) and i recently got another, goose (6 months f). he was very wary when i first brought her home. which is understandable considering he was the only cat until that point. the issue is sometimes he will come up to her (when shes minding her own business) and start like hitting her on the head and meowing. not like he meows for food but like a long angry meow. i always try to break them up. i also make sure to give suki lots of love always so he doesnt feel pushed aside. i also have checked her head to see if he scratched her but in the past 5 and a half months he never has. i think hes not using claws and just his paws but should i be concerned it could escalate? i let him in my room with the door shut so he has alone time with just me and he is very affectionate with me most of the time but hes my first cat ever so im not sure if i should be worried or not. hes very much a scaredy cat and doesnt like to be handled unless its my mom or me. will he get used to her or should i try to keep them apart?