Tweeting about the injury, the Ulster lock confirmed: "I did the injury as soon as I came on but was too pumped to care. The messages of support have been class, thanks folks!"
He underwent surgery in Belfast today to 'stabilise the fractured radius' in his right arm. According to a statement from Ulster Rugby tonight, Tuohy is expected to be out of rugby for 'between eight to ten weeks'.
"(Had) op this morning, Ulster Hospital have been great. Gutted to miss the rest of the Six Nations, but there's a game in eight weeks...," tweeted Tuohy.
With the province's Heineken Cup quarter-final clash with Saracens just under eight weeks away, the 28-year-old is in danger of missing the Ravenhill tie.
But he will hope to follow in the footsteps of his Ulster and Ireland team-mate Rory Best who made a quicker-than-expected recovery from the fractured forearm he sustained against New Zealand in November.
Best was back in the white jersey of Ulster against Montpellier on January 10 - less than seven weeks after the defeat to the All Blacks.
Meanwhile, Ulster picked up a couple of injuries during their 10-7 RaboDirect PRO12 win over the Ospreys last Friday night.
The province's statement added: "Darren Cave suffered a hyperextension injury to his left knee in the Ospreys game. He sat out training today but is expected to be available for next Friday's match against the Scarlets.
"Lewis Stevenson sustained a forced flexion of his neck against the Ospreys. He was scanned today and will be reviewed later in the week to determine his availability for the Scarlets game."