Hello, the explanation of your problem is not that clear to give you best advice but still I think I can help. Young age active guys who does gym and who run mostly they experience lower leg pain due to tightness of muscles. Proper warm up, stretches an cool down will help you. Give more importance for improving your flexibility and strength. And before that meet a physio and make sure the problem is not becoz of any other reasons..
Next Steps
consult a physio
Health Tips
continue to be active with gym n running.. but well designed exercise program based on fitness evaluation is must.