Is this a good idea? massaging my friend...?

[Dave]

So i'm gay, 18 and my best friend has known since i was 16, i use to like him and he knew that aswell and he got me through allot of hard times so we're very close...

Anyway we started uni this year and he's doing a degree in physiotherapy...on Monday they have their first practical which involves massaging each other and feeling each others muscles...which makes me pretty uncomfortable...

So anyway he let me feel like his legs, arms, back etc...and then today he let me massage his back for about 10minutes, then he did mine for about 10 and then i massaged his feet for another 15minutes...Do u think this is a good idea?

Also...i'm not sure but i'm pretty sure after the foot massage that he had an erection...(just looked like that in his pants lol...) and i'm certain he's straight...but could that just happen just randomly lol...like not because i'm a guy etc?
I can't exactly ask him can i? have you any tact? If i asked him he would say no and never let me do it again. He is very very shy and doesn't like very personal questions, especially about his penis etc..
Also he was sitting on my bed...his feet on me, i was sitting at the other end...on his ass leaning back...