My iphone's screen cracked and part of the touch screen stopped working?

my iphone was alredy cracked before but just minorly at the bottem, so while i was out with friends last night i guess i jumped and while it was in my pocket it hit my kneecap and basicly it just cracked even more, so then i tried unlocking it and from where the deepest like center crack is, which is like in the middle of the phone, all the way down the touch screen doesnt work, but like if you press home twice and want to play a song that part of the touch screen works. basicly what im asking is what i should do and if i should repair it would i need to replace the whole lcd or just the glass and how much would that cost. thank you