Ouch! I'm sorry about that!
I had open heart surgery some time ago, and this question had plagued me for years!
If you have light colored skin, in time, 3 - 9 months, the scar will noticeably fade and disappear. Perhaps in time, you won't recognize it at all? If your skin is dark, it may last forever.
If you don't want to wait that long, there are products specifically formulated for scars. One I used is called "Mederma" Scar Treatment. It's sold at most drug stores, and is about $10 a bottle. It's an ointment that you have to apply daily. I also tried some different products. Some scar removal products require you wear a "patch" over the scar for 18 hours a day or more.
The one thing I learned, is that you don't want the scar to dry. When it is dry, it is more prone to becoming permanent, or taking longer to fade. If you don't want to spend a lot of money, you should put some Vitamin E oil on the scar, to prevent it from drying out. That'll help it heal faster.
But,.. if you don't mind spending a lot of money to have it go away, you can go to a cosmetic surgery clinic and ask the doctor for a "Steroidal Scar Treatment Shot." It's a type of steroid that is injected into the scar with a needle. A bit painful, yes. The doctor inserts the needle directly into the scar and pushes it around as it injects the serum. Within the first minute, it is already working, and by the 4th day, the scar is all but completely GONE. I kid you not! The down side is, it costs $100 a shot.
Ok then! Hope this helps.