Don't try to send any DMs for at least 24 hours. If after 26 hours you are still blocked, lay off for another 24 hours. If after 50 hours from the initial block, you are still blocked wait another 24 hours. If after 75 hours you are still blocked, it's usually a 7 day block by IG.
Lay off for 7 days, if after 7 days, you are still blocked, contact Instagram.
Instagram usually goes on blocks in this way, 1 x 1 x 1, then 2 , then 3, then 7 days for infractions.
After they let you back, stop messing around with DMs. Long blocks means you've been banned before. Usually next ban, will be a deletion of your account.