You have two issues. 1) whether you had proper permission to widen your driveway and 2) if you did, whether you can prove it.
You say that you got permission to widen your driveway, but you do not state who granted you that permission. If you had a written agreement allowing you to do this, there should be two parties with that agreement. One is you, and the other is the entity that signed the agreement. This may be the HOA or whatever entity had authority under the CC&Rs if the HOA had not been formed yet. If you lost the paperwork, try to contact the other entity that signed the agreement to see if they have record of it. Typically, they would be required to keep the paperwork for a certain period of time.
The documents which likely govern your rights here are the CC&Rs (Covenants, Conditions, & Restrictions) and potentially the HOA rules. If the CC&Rs did not exist when these events transpired, you would need to find another development document that existed first. Sometimes making an exception to the CC&Rs requires a certain percentage of approval from the other lot owners. I would need more detail before I could give you an answer one way or the other. Basically, you need to determine whether it is worth it to you to pay an attorney to determine if you have the right to your driveway, or whether you would rather bring it into "compliance" with the general covenants.