My son was born with what looks like to me a birthmark on his forhead?

Ok so my son is 17 months old now and since he was born he has this mark on his forehead which his doctor calls it angel kisses. I looked it up recently and it is a salmon patch and it is pretty common and says it should go away by the time they are two. It is getting lighter and most people cant even tell unless he starts crying or gets mad then it gets redder. I was just wondering if anyone knows what I'm talking about what if it doesn't go away is there anything I could do. I love him him so much . I don't want to sound like a horrible mom because I wish it would go away