What Causes Hearing Problems, Headaches And Insomnia After A Brain Surgery?

i had brain surgery 1 year ago for a posterior fossa cyst and i am recently experiencing hearing problems, headaches, insomnia and i have noticed i have swollen lymph nodes on my neck. Also i think i have a lump at the back of my neck along my incision. Is it possible to develop a malignant brain tumour following my surgery?