If you have access to phpMyAdmin, you can reset user permission from database. But first thing first, t proper ake backup of your wordpress database.
In phpMyAdmin, locate your wordpress database and find table called wp_usermeta. There is a setting for your admin user's priviledges. You will find a field that contains something like:
You must change it to:
After saving your changes in phpMyAdmin, now try to login to worpdress dashboard.
Another and better solution is to create a new user with admin privillege via phpMyAdmin and then change your original user role from Wordpress Admin Dashboard. Here is a nice guide for you. I would recommend you to go this way.
If you are not comfortable doing this, please ask your webhost if they can do this for you.