C162 pilot reported a loss of control due to the aircraft's entry door opening in flight after not being properly secured. Pilot returned to departure airport and landed.

Narrative

We were conducting a personal flight from ZZZ to ZZZ1. No anomalies were found during preflight. We performed a run-up on the ramp; got a clearance; and taxied to the assigned runway XXL. After stopping at the hold-short line I started performing the pre-takeoff checklist but was interrupted by tower instructing us to line up and wait on [runway] XXL ('Aircraft X runway XXL line-up and wait'). We taxied onto the runway and got our take-off clearance immediately after getting into position. I completed the checklist item I had started earlier and advanced the throttle for takeoff. After an uneventful climb and approximately 5 minutes of flight at cruise altitude (4500 feet MSL; 3500 feet AGL) at about 95kt TAS the aircraft performed an uncommanded and rather violent roll to the right and pitched up significantly. I instinctively pushed the yoke forward; leveled the wings; and ensured proper airspeed. I realized that the cause for this behavior was that the left door popped open. The Cessna 162 has wing doors that allow for easy entry and exit but require two door latches to be secured (one at the rear end and one at the front end). I realized that when allowing myself to be rushed into position on the runway I skipped part of the take-off checklist; which included checking that the second door latch is secured.We immediately turned back towards ZZZ and [advised ATC]. We were cleared for runway XL. The added drag of the open and bent door required us to trade altitude for speed even at full throttle. We managed to arrive at short final for [runway] XL with about 500 feet of altitude left. After a successful landing we taxied back to the hangar to evaluate the damage. The door was folded up halfway since the rear latch held (but eventually failed) while the front of the door opened due to the unsecured latch.I made the mistake of not completing the take-off checklist before entering the runway. I should have declined the line-up and wait instruction and instead go through the checklist items before contacting tower. The sense of urgency the received instruction conveyed led me to rush the normal take-off procedure. In the future I will decline such an instruction in the event that I am not fully ready for take-off yet; even if that causes a delay for my departure and the departure of following aircraft. More broadly; it is a reminder that I am responsible for the safety of the flight and have the right to decline any clearance and instruction provided by ATC to ensure a safe outcome.I realize that the unusual attitude training received during my recently completed primary training has helped me handle the situation once it arose. I did not hesitate to advise ATC and was ready to land in a field in case we would not make it back to the runway.