Profit center issue

Hi All

We have some materials ,initially Profit center not maintained.

We have posted GR agianst PO 101,

After that trying to Post Goods Issue error

Balancing field "Profit Center" in line item 001 not filled

Message no. GLT2201

We go to MM02 and trying to enter Profit centre at Gen plant data 2 screen  again error

You want to change the profit center but material stock still exists

Message no. MM335

We try to reverse 101 MIGO document  error

Balancing field "Profit Center" in line item 001 not filled
Message no. GLT2201

Please help how can I enter Profit center in MM02

Thanks

SAP MM