But how exactly will a orc kiss his partner without stabbing him?
They'd likely have a different way of showing such affection, as said not all would kiss to do that.
For humans kissing is quite obvious, after all we got a pretty good sample size here in the real world
. There could however be cultural difference between "kisses".
For Khajiit as mentioned rubbing head together could be that, our cats to that when they show they like you.
Argonians could rub the tip of their muzzle against their partners cheek, a high sign of affection would be if they fully close their eyes, real reptiles show that they feel safe by doing so.
Elves would likely be quite similar to humans in that matter but again with a few cultural differences.
A Orcs sign of affection could very well be just holding foreheads together but I don't really know too much about their culture.
In fact there could be in game books that detail some of the affection signs between races, species and cultures, studying those can give you some knowledge about how you can greet people more correctly and, in a wider sense, some "flirting" tips (As mentioned somewhere else, flirting could be used to buy yourself people's trust).