Injury after performing shrugs

Three weeks ago today, I was performing shrugs at the gym and felt a slight cracking noise within the collarbone area. Anyway, I didn't stop. I finished those remaining reps and then performed one more set with extra weight. The next day my trapezius muscle felt sore and so I decided to rest until it got better. The pain radiated to my neck, collarbone area and a little to the triceps. Three days after the injury I trained my biceps and triceps and felt fine on every exercise except bicep curl with the barbells. I haven't trained since as I have been sick with the flu and been quite busy but three weeks since the injury and my trapezius muscle still feels a little sore. It feels a little better than before but it still isn't 100%. Does anyone have any idea on what type of injury I may have sustained? Does this sound like a big problem to you? I'm sure I can train on this but I don't want to in case I end up making things worse. Thank you & god bless.