Is it normal after radiation therapy to make your legs feel weak and sore?

yes

Explanation:

Radiation-induced fibrosis is the most common late effects of radiation therapy; affecting up to 80% of irradiated patients. In skeletal muscle, radiation-induced fibrosis result in muscle atrophy, weakness, impaired mobility, increased morbidity and disability, and reduced quality of life.

Yes, it is a side-effect to have tingling, weakness or loss of sensation in legs. This is called radiotherapy induced lumbosacral plexopathy (RILP)

It usually lasts 3 to 4 weeks after your treatment stops.