Not only would I loosen the lower yoke pinch bolts but also the wheel spindle (or clamps) and also the mudguard bridge fittings (if appropriate).
On many bikes the steering stem nut would also need to be loosened but is probably not necessary in this instance as the stem sleeve nut will turn with the top yoke.
After slackening everything, sit astride the bike and apply the front brake, then vigorously pump the forks, this should straighten them, if not they can be levered gently as TBS mentioned, or do this by holding the front wheel between your legs and twisting the bars until everything lines up.
If repeated attempts won't get everything to line up then something could be bent (stanchions, yokes etc.) and further investigation will be necessary.