1988 GMC Sierra Question about a sound.

I have a 1988 GMC Sierra 4X4 and recently when driving on the interstate, I spun out on ice and through the center ditch. I didn't hit anything, but when I got back on the road a loud thudding sound was coming from my left front tire. I pulled over but it wasn't flat, the tire was fine. At first it only made the sound in 4-wheel drive but now the sound is happening in 2-wheel drive as well. I took it to a mechanic but they only could do a quick check at the time and everything on the outside and tires seemed fine. I was just wondering if you had any ideas on what the problem could be. Thank you.