These are common enough problems in dogs and usually manage to repair themselves.
Other common causes are splinters and thorns and broken toe nails which are not a concern as long as we attend to the cause and remove splinter and thorns etc they usually heal on their own.
The time to be concerned is when a dog continues to limp and the cause is not apparent.
Recurrent limping is also something to take seriously. In these cases then you should involve your vet.
Vet checkup
It is always best to veer on the side of caution when it comes to your dogs prolonged or recurrent limping. The vet will initially check for swelling and joints for pain and heat.
It’s useful for the vet if the owner can divulge any history like when he started limping and what had occurred recently to the time he started to limp.
He will also check him for thorns and check between his toes to see if anything there causing pain and giving the dog a limp.
He will check the pads for cuts or pices of glass etc. cuts and lacerations can be treated by washing the feet in hydrogen peroxide or Betadine which does not sting like iodine would.
Dogs are fairly robust and their own licking and time will heal a mild cut but if the laceration is deeper then it could be infected and the vet will recommend a course of anti biotic.
Nail care
The care of the toenails is important as overgrown toenails can break revealing a quick cut that can become sore.
The vet will check for warts and grit checking the inside of the toes thoroughly as pads are as tough as they get but between the toes is a haven for bacteria and infection and can cause him to limp.
It’s helpful to encourage your dog to run around and play on concrete as this naturally files down the toenail but if he does not have that much level of activity then simply ensure he has his toenails clipped regular.
Over grown toenails can also cause the dog to twist his joints in his foot and this could be resulting in pain and limping. Dogs lick there paws and this can cause infections between the toes.
Arthritis
The vet may check the elbows for signs of arthritis which is fairly common especially in an older dog. He will check for elbow dysplasia and osteochonritis dissecans. Same with the shoulders as osteochonritis dissecans can affect them too and if serious enough may consider surgery.
The vet can even tell by examining the wear and tear on toenails of what the problem could possibly be. By putting more weight down on his good limb the vet may be able to see what it is he is compensating for with his awkward gait.
Watch his walk
Watching your dog walk can reveal a lot as when he walks he will put extra weight on his good limb to compensate his bad one and if u observe him lower his head as he bears down his weight and lift it when on the painful limb. The vet may want to x-ray a particular problem area and in many cases will x-ray the same joint on the unaffected leg, as comparisons are helpful for the vet to make a diagnosis.
In short the obvious things to look for like cuts and grit and thorns is an obvious first thing to do, but in any case that a limp does not go away for after a slightly prolonged period of time or recurring limping, then get him checked.
A helpful guide and source to reliable information related to your dog limping is here.