Thanks for writing in,
Where is it hard?
Is it still within the sheath?
Is there a double knot like structure on the base of the penis?
Is it bothering him, is he licking at it or having trouble urinating?
When was he neutered?
Has he ever been breed?
It is not within the sheath.
The pink part is protuding which was something we had seen on rare occasion previously but now is a constant.
He was neutered when he was two.
There is no double knot at the base.
He has been licking but does not seem to be having a problem urinating.
He was never breed.
Ok, thanks for that added info!
Sometimes dogs can have a problem with their penis where in the case of a Peke it would be hanging out about 4-5 inches and as big around as almost a hotdog bun! This is what his erect penis would look like. The double knot I was referring to would be the boulborethral gland (spelling??) That is also also a normal structure and you could possibly see that even now if he got really excited. If the part you are talking about is hanging out 1/2 inch up to about 1 1/2 inches, then this is normal. Some dogs penis' may hang out alittle bit. If it is dry and absolutely won't go back in, then you may want to bring him to your vet so that he can lube it up and pull the sheath back over it. He will also look at it to ensure there is no mass or lesion further down on the penis that you can't see that is making it impossible for it to pull back in.
I hope this helps, but I really think this just may be normal for your dog and not really a problem. It just doesn't look pleasant!