Araujo left the field in the 67th minute after clashing heads with teammate Gavi and was sent to the hospital to undergo further tests.
The victory saw Barça tighten its grip on second place in La Liga by moving seven points clear of third-placed Sevilla.
Memphis Depay opened the scoring after a brilliant piece of skill from Ousmane Dembélé and Pierre-Emerick Aubameyang doubled Barcelona’s lead just before halftime — despite being outplayed for much for the first half.
Shortly after the break, Aubameyang scored again following another assist from Dembélé, but a misplaced pass from goalkeeper Marc-André ter Stegen then allowed Iago Aspas to pull one back for Celta.
Hopes of a comeback, however, were dented soon after as Jeison Murillo was sent off for a challenge on Depay.
There was then a lengthy break in play as Araujo received treatment before being taken off the pitch in an ambulance and replaced by Clément Lenglet.
“Today, we did things well. Maybe, the first half was a bit complicated, but in the second, it was much better,” said Aubameyang.
“That’s positive for us to continue fighting for this second place.”
Asked about Araujo’s condition after the game, Barcelona manager Xavi said the defender is “okay” and would stay in hospital overnight.
Barcelona has two league games left this season — against Getafe on Sunday and Villarreal next week.