I have localized fasciculation on my shoulder below collar bone and above armpit for two weeks and it won't stop. it started after minor injury which healed but twitching won't go away, constant at rest. worried about als of course. should i do emg?

Since your symptom began after a specific injury, I don't know why ALS would be a concern. EMG is probably the most useful technique to identify the muscle that is spasming, and then the specific nerve. Based on the area you've identified, possibly the pec minor, or pec major. Once identified, various modes of physical therapy can successfully treat.