How can I tighten up my legs?

I am 17 years old, 6'1" I weigh 225. I have been big for the past few years. However, I have lost 40 lbs over the past few years. My legs are REALLY flabby. Is there any way that they will tighten up fully? Will my skin stretch back? I exercise daily, running. What can I do to tighen my legs?

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