My son has vitamin b12>1000 , d3 17 and ferritin of 10, he is 4 years, anything to be concerned?

Very much so: The B12 means nothing. The ferritin is a bit low; is he getting enough iron in his diet?If you're raising a young vegetarian please be careful. Meat is his best source especially while he's growing; or there are supplements. If we are using the usual units for D3, this is very low. If he's not drinking vitamin D fortified milk, can you get him a supplement / get him out into some sunlight?