Hi thanks for your question.
you have got removed your ovary ,tube (side not mentioned)along with large dermoid cyst
.and now you have mass on left lower side with some pain on left side and back.
If your cyst was not removed completely at that time ,it could be recurrence of dermoid mass.
But if that mass was removed completely, then it can be a new growth.
Benign or malignant can be determined by doing ultrasound
of the mass and if need arise CT guided biopsy
of this mass,
Don't worry there are more chances that it can be a benign swelling.
Hope i answered your question