You can use Oracle Enterprise Manager Database Express (EM Express) to remove the quota limitations for the user Nick on his default tablespace, USERS. To do so, you must modify his user account.
To modify the user Nick:
In EM Express, go to the Users page, as described in "Viewing User Accounts".
Select the user account NICK, and from the Actions menu, select View Details.
The View User page appears, with the Privileges & Roles subpage displayed.
Click the Quotas subtab.
The Quotas subpage appears.
Select tablespace USERS and then click Edit.
The Alter Quota page appears.
In the Quota field, enter Unlimited.
Click OK.
A confirmation message appears.