Pink hy phlegm with blood?

Last night I could feel my throat slowly getting irritated but I went out anyway.. When I got home the back of my throat was filled with phlegm... I was not coughing much but needed to spit constantly. I was spitting up white hy phlegm alot and all a sudden just ONE TIME ONLY i spit out pink hy phlegm with thick blood in it... (it kinda looked like strawberry milkshake with blood lol) after that it was back to white... It was really odd so I googled it and alot of site say it could be dangerous and to go to the E.R immediately.. but see it only happened once.. It wasn't a continuous thing... What should I do? I dont wanna go to the doctor's if it is not something serious.... Like I said it only happened that one time and back to white so should I still be concerned??? I would really prefer someone who works in the medical field on this one question please... Thank you!!!