Now that i have Tamron 17-50mm, should i sell my 50mm f1.8?

Now that i have Tamron 17-50mm, should i sell my 50mm f1.8?
if so, what's next to buy?

I currently have Nikon D90, Tamron 17-50mm non VC and 50mm f1.8

Keep your 50mm f1.8 for low-light photography. Its 1-1/3 stops faster than the 17-50mm f2.8.

Before buying another lens you first need to decide why you need it. How is your photography being limited by the 17-50mm lens? What would you like to photograph that you can't with the 17-50mm lens? So decide why you need a lens and how you'll use it before buying.

Never sell your primes. That 50 is the lightest, fastest and sharpest lens you own. If you're looking to sell, get rid of the Tamron.