The 26-year-old had an operation after breaking the radial bone in his arm when three explosions went off as the bus made its way to the stadium shortly before Dortmund's Champions League clash with AS Monaco.
"The pain, the panic, and the uncertainty of not knowing what was going on, nor how long it would last... they were the longest and hardest 15 minutes of my life," the Spain international wrote on Instagram on Friday.
“About all of that I want to tell you that I think the shock of those days is easing all the time and the desire to live, struggle, work ... play (and) train ... is getting stronger."
"What do I feel when I look at my swollen and badly damaged wrist? I feel pride, thinking that all the harm they wanted to do to us on Tuesday led to nothing worse than that."
The accompanying photo showed Bartra looking toward his family. He had a cast on most of his right arm and around his left wrist.
Dortmund said on Thursday that Bartra, who joined the club for 8 million euros ($8.50 million) from Barcelona at the start of the season, should return to playing in "about four weeks".
Tuesday's match was rescheduled for 24 hours later and Monaco secured a 3-2 victory over Dortmund, who will next host Eintracht Frankfurt in the Bundesliga on Saturday.
German newspaper Bild said on its website that Dortmund's stadium program for the weekend game featured a message from the club's chief executive Hans-Joachim Watzke saying: "Like on Wednesday evening in the game against Monaco, we're not playing just for ourselves today.
"We're playing for everyone. We wanted to clearly express that terrorism and hatred should never be allowed to determine how we behave.
"It's up to all of us -- the players, officials and fans in equal measure -- to show society that we won't give in to terrorism.
"And of course we're also playing for Marc Bartra, who wants to see his team win!"
On Thursday, a German judge authorized the arrest of a 26-year-old Iraqi man, who was detained after the attack and prosecutors said they believed he was a member of Islamic State.
The prosecutors, however, said there is no evidence he took part in the attack in Dortmund.
A spokeswoman for the federal prosecutors said on Friday there was no new information to give.
(Reporting by Hardik Vyas in Bengaluru; Editing by Toby Davis)