Unsure if I should be worried about this growth on skin

My dog has had this a very long time, when I brought him to the vet and mentioned it they didn’t say anything about it. Though would this be dangerous? 

Hello - I wonder whether your vet felt that this lump was a wart, caused by a  papilloma virus - however, I have not examined your dog and there are other possibilities, so please confirm it with them.   Frequently, warts are relatively harmless in themselves and often regress again; however, they can spread between dogs, particularly where toys etc are being shared, so it's worth asking your vet whether additional steps are worth taking. https://vethelpdirect.com/vetblog/2020/10/17/why-does-my-dog-have-warts/ Young dogs have weaker immune systems which can explain their picking up a wart; older dogs are prone to pick up warts at times of other bodily or mental stress (which imacts on the immune system , which normally prevents warts taking hold) so vets will often want to do a full examination / ask questions about other body systems that seemingly do not related to the wart at this time. I hope that something there helps.

My apologies, I will reword that to make it more readable. This may be a wart, caused by a papilloma virus (your vet should be asked to confirm this as they have examined your dog in person and are responsible for their care).  If this is the case, it may be relevant in that a) these can be transmitted to other dogs, especially those with poor immune systems - so there might be steps you could take to prevent spread, depending on your dogs' situation  and b)  when older dogs develop warts, it is sometimes because their immune system has been weakened and 'let them in,' so a full-body check-up is usually a good idea.  I hope that something there helps.