More details needed. Road or mountain bike? Did you just just removed the wheel (with tire on it) from the fork (like for transporting), or did you mean you pulled the tire off the wheel rim and replaced it (like repairing a flat)?
Some tires (especially more aggressive mountain bike tires) are directional - did you put the tire back on the same direction it was before? If you did not take the tire off the rim and did not remove the skewer, the skewer clamp should be on the left side of the fork (non-drive side of your bike).
If nothing else, flip your bike upside-down and re-seat the front wheel making sure it's to the bottom of the dropouts on both sides, then make sure the skewer is good and tight.
If you think you may have put the tire on the wheel backwards, remove the wheel and flip it around so the skewer is on the right and see if that makes any difference. If you have disc brakes this won't work, you would have to remove and tire from the wheel to change the direction.