Yes you can certainly see delayed onset muscle soreness (DOMS) changes on ultrasound and if it progresses further you may diagnose rhabdomyolysis.
With DOMS you will have a clinically swollen and (tight) firm muscle following excessive exercise. It will be tender on palpation.
The sonographic findings are that the muscle will be swollen compared to the contralateral side and the muscle will have increased echogenicity.
It is a diagnosis I make regularly.
If you watch the MSK pathology principles webinar on the website you will see examples.
Rhabdomyolysis has similar appearances, however you will see cystic areas appearing from the muscle breakdown and if you take blood they will have an elevated creatine kinase (CK)
For myofascial trigger points I have nothing to offer sonographically.
You can use your clinical skills, but the ultrasound does not help in my hands.
I would bet someone is exploring the use of elastography to identify these points !!!
You can count me as a sceptic with many of these applications of elastography, but I am open to being convinced if the evidence is strong.