That is a prolapse... sometimes it'll go back in on its own, if it doesn't with in a very short amount of time, it can become necrotic from cut off blood flow. I would recommend having a vet look at it... it should be an easy fix if you get him in asap. Perhaps a senior member can recommend a home remedy.
Soak his bottom in sugar water. I do not know the proportions but you may be able to find them by doing a search of the forums. Also if it does not go back in on its own you need to keep it moist using KY Jelly or another water soluble lubricant until you get to a vet.
So we went to the vet today and he had a slight prolapse and A LOT of seminal build-up causing a sever impaction. Does anyone know if this kind of thing can be removed safely at home or should i leave this to the vet if it happens again.