If x-ray and endoscopy
has not shown the presence of fish bone,it means it is not there.
The symptoms of pricking sensation and droplets of blood are due to the lacerations
and micro tears in mucosa of throat.
Had the fish bone been in your lungs,you would have had breathlessness and bouts of violent coughing.
Wait and you shall see the symptoms disappearing over the next few days as the damaged mucosa gets healed.
No treatment is required at the moment.