Tamron AF 70-300mm F/4-5.6 Di LD MACRO 1:2 - tripped and knocked lens, small part rattling inside, telezoom won't work

SOURCE: Detaching Lens Hood

I'm not sure of the exact model number of your lens, but the hood should have a bayonet flange and rotating it in one direction or the other should allow it to then simply pull off.

SOURCE: Tamron 200-500mm F5-6.3 SP AF

Assuming the lens has a Nikon mount, yes.

SOURCE: Drop my Nikon D100 camera with a Tamron AF

First question "is it worth repairing" if it were mine I'd look to see what a new one is worth then divide that in half (cause that's what you might be able to buy a used one for) then figure about $120.00 for cleaning lubricating and adjusting the your lens. With your lens you know what you have, buying used might need the service. you are the one to decide. As for the second question "can I repair it myself" short answer no. If you have to ask if you can repair it then you don't have the necessary tools and general knowledge of how to dismantle and reassemble the lens (and have it work when finished). The lens took a hit and most likely set the inner and outer lens barrels out of alignment causing the inner barrel to slip out of its seal and or focusing gear and hang things up forcing it will break parts causing more repair costs. All else fails get an estimate before repair. Been there with a lens myself and after a couple a months without bit the bullet and had it repaired. Cheers best of luck

SOURCE: tamron AF 18-200MM XR Di II LD dust inside; how do I clean?

Dust and other small debris is drawn into the lens due to the vacuum created when zooming in. You can reduce the chances of drawing in dust and debris by slowly zooming in as opposed to rapidly zooming in.

Now that you how it gets in and how to help prevent it from getting in again, comes the bad news. There's really no way to disassemble the lens to clean it up at home. These are precision optics with many small moving parts that really need to be serviced in a dust free environment. You best bet it to contact Tamron (or authorized servicer) to learn how much it will cost to be cleaned by them. This will keep the warranty (if any) intact, too.

Good luck!