How do I convince my bf that his s are normal and expected...he is embarred?

I started dating a really neat guy a short time ago...he gets hard really easy and then gets red faced, embarrssed and really flustered...On our first date, I wore the tightest, skinniest jeans I have, a really skimpy tight fitting cropped top, and a pair of medium heels...I wore the this outfit because it is tight and it exposed my lower back tattoo which he did not know I had at the time...anyway, he saw it that night...at one point, I somehow, maybe accidentally on purpose dropped my cigarette and had to bend over to pick it up...this exposed my and my tat more than normal and I noticed he got very hard...I said to him..looks like something is getting a little, big down there, did I cause it?...he got red faced and embarrased and said he was sorry...well, the thing is I wore this outfit to get him worked up and apparently it did what it was supposed to...I asked him...was it my tight pants or my tattoo..he just said yes and but did not talk about it anymore...how can I convince him I wore the outfit for this reason and this is the way I wanted him to react...I don't want him to be ashamed