The Polish football association confirmed the injury on Friday, saying that the player "accidentally fell on his left hand" while training with his fellow countrymen in Jastarnia.
Wszołek has since undergone surgery but will be out for approximately three months, even with the operation going perfectly.
Road to recovery begins
Speaking to Sportowe Fakty, Dr. Martin Redman, an orthopedic surgeon who performed the operation on Wszołek, explained the situation of the player's injury.
"Everything went smoothly," he confirmed, explaining that "swelling" is usual after the operation and so massages and cooling of the injured area will be on the schedule for his early rehabilitation.
"In the event of such a breach, recovery takes about three months, but we will do everything possible to come back earlier," Dr. Redman added.
Wszołek has had his arm immobilised at the elbow to avoid rotational movement, and on June 2 he will have this reversed. After that, he can step up his rehab.
The next two months of his recovery will be spent in his homeland, in Warsaw, and then doctors in both Poland and Italy, where he plays his club football, will look at what his treatment needs next.
Big blow for the youngster
This injury is a massive blow for Wszołek, who looked set to go to his first major tournament as a senior international.
The 24-year-old has played in major tournaments for Poland's youth teams, but has now started to make his mark on the first team too.
Wszołek earned his eighth cap back in March and marked it with his first goals too, scoring twice in a 5-0 victory over Finland.
He hasn't had great success at club level this season, joining Hellas Verona on loan from Sampdoria and being relegated to Serie B, and so the summer's big event was a chance for him to put himself in the shop window too.
He made just six appearances for Sampdoria last term, forcing him to look elsewhere for game time, and whether he will get more chances with them in the new season remains unclear.
However, for now, Wszołek's focus is on recovering from injury and then on the 2016-17 campaign, where he'll hope to be earning more call-ups for Poland after a promising start to his senior career with them.