Yes, God certainly cares what you do because He loves you and doesn't want you to do something that will harm you or send you down the wrong road in life. He has said, "I have loved you with an everlasting love" (Jeremiah 31:3).
But God not only cares what you do. He also knows what's best for you, and He wants to show it to you. God isn't an unconcerned bystander, just hoping that somehow you'll make the right decision. He wants to guide and help you, and that's why the most important thing you can do is turn to Him and ask Him to show you His will concerning this decision.
How can you know God's will? The first step is to put yourself into His hands by asking Jesus Christ to come into your life. He came into the world to erase the barrier of sin that separates us from God, and He did this by giving His life as the final and complete sacrifice for our sins. The most important decision you'll ever make is to commit your life to Him.
Then ask God to guide you as you make this decision. How will He do this? Often He guides us by His Word, the Bible; He will never direct you to do anything that's contrary to His Word. He guides us also as we pray and seek His will. He also may use wise friends to help us. You can trust His promise: "Trust in the Lord with all your heart... and He shall direct your paths" (Proverbs 3:5-6, NKJV).