The 22-year-old collided with Dragons teammate Sam Parry and was taken to Morriston Hospital in Swansea as a precaution with his fitness for the upcoming autumn internationals now in doubt.
Wales play South Africa, Argentina, Tonga and Australia at the Millennium Stadium next month however Dragons head coach Jones wouldn't comment on the seriousness of the injury.
"The incident looked fairly innocuous on video. Toby was struck him in the head area and has suffered an adverse reaction," said Jones.
"Strict precautions were taken, with a lot of numbness down his left hand. We're fairly optimistic but we don't want to pre-judge anything."