Thanks for posting your query.
With the available described symptoms, there appears to be possibility of acute viral fever
Presence of rash, fever with body ache
suggest the diagnosis.
As such there appears to be no correlation between present symptoms and lead poisoning
You should consult with your treating doctor/ internal medicine specialist and should go for thorough check up.
You should go for ultrasound
imaging of lump at the back of neck.
Meanwhile you should take proper bed rest along with analgesics and muscle relaxants.
Dr. Mayank Bhargava