Ok!
So i just got this solved by support. 

There was a category for this project witch was stale. 
So support used a script called remove_stale_entries.py. 

CAUTION!
Use this only after verifying with support that it’s safe. But for CE users, it might help :)

import env
import argparse
from insights_interface.insights_interface_pb2 import *
from insights_interface.insights_interface import *
interface = InsightsInterface('127.0.0.1', 2027)

parser = argparse.ArgumentParser()
parser.add_argument("--uuid", nargs="*", required=True, help="Enter stale entity's UUID as a list separated by space", default=a])
parser.add_argument("--entity_type", required=True, help="Enter the type of entity. Example : task,vm etc. ")
parser.add_argument("--cas", help="Use this flag for deleting CAS entities, else deletion will fail", action="store_true", required=False)

if len(sys.argv)==1:
    parser.print_help()
    sys.exit(1)

args = parser.parse_args()
entity_list = args.uuid
entity_type = args.entity_type
cas = args.cas
g = GetEntitiesArg()
for entity_id in entity_list:
    e = EntityGuid()
    e.entity_type_name = entity_type
    e.entity_id = entity_id
    g.entity_guid_list.extend(te])

res = interface.GetEntities(g)

if len(res.entity) == 0:
    print "No entities found matching the input UUID(s)."

for entity in res.entity:
    d = DeleteEntityArg()
    d.entity_guid.CopyFrom(entity.entity_guid)
    if(cas):
        d.cas_value = entity.cas_value + 1
        print 'deleting entity %s with CAS %s' \
            % (str(entity.entity_guid.entity_id), entity.cas_value)
    else:
        print 'deleting entity %s' % (str(entity.entity_guid.entity_id))
    interface.DeleteEntity(d)

put the script i /home/nutanix/bin

chmod 777 on the script. 

Then used nuclei project.list to get the UUID from the undeletable project. 

Then ran the python script:

python remove_stale_entries.py --uuid 857fbbf0-3ecc-5d9e-b4b4-f9b4b54d8192 --entity_type=abac_category --cas
tada, the project is gone :)