Hello & welcome,
Failure to wear the retainer given to you by your dentist
after finishing orthodontic treatment, makes the teeth to move back to their original locations in due period of time.
This happens because our teeth are held in the position by elastic periodontal fibers which require to set at new position after treatment & so wearing retention plate after the treatment is mandatory atleast for 6 months.
If this is the case, then having pain your teeth is quiet normal as those elastic fibers are being stretched again. But, this will revert back & pain will definitely subside within a week after starting wearing of retention plate.
The more i am concerned here is by the swelling you got on the lips & i think intake of Ibuprofen
might be culprit for this. Because there is no direct relation between retention plate & swollen lips. But still, you should visit your dentist as soon as possible for clinical examination.
Avoid use of painkillers & use those drugs only if dentist prescribes it to you as some painkillers interfere with bone resorption
process which inturn intervenes teeth movements.