I accidentally deleted a contact how do I get it back

If you have deleted a contact and want to restore it, you can sign in at https://icloud.com, go to Account Settings, scroll down a bit and find the Advanced menu. There is an option called "Restore Contacts". that feature can often help if you have accidentally deleted your contacts.

Read more here:

If you accidentally deleted your calendars, bookmarks, or contacts from iCloud - Apple Support

The advise to restore in iCloud, acc settings applies, only if you chose to sync contacts in iCloud as well. Otherwise, “contacts deleted by mistake” are completely removed.