What Causes Itchy Red Swollen Round Bump On Neck?

Hi, ok one morning i woke up wit a big red swollen round bump on my neck and it was pretty itchy, not very, but it was itchy but i didnt scratch much. the swelling went down and it turned into a dark brownish bump. everyone is suspecting it's a hicky and i admit it does look like one but it's NOT, i swear. i had a gymnastics competition yesterday, and with all the stress and adrenaline rushing through me, it is now bright red, not hard to miss at all. it kinda looks like those red birthmarks that some people have, just not that extreme. i dont noe what it is, everyone thinks it's a hicky but i really don't want people assuming that though it looks EXACTLY like one. any ideas on what it is please?...