user = models.OneToOneField(User, on_delete=models.CASCADE)

join_date = models.DateField(default=datetime.today())

end_date = models.DateField(default=datetime.today() + timedelta(days=7))

package_status = models.BooleanField(default=True,blank=True)

phone_number = models.CharField(max_length=30, blank=True)


idboard= models.CharField(max_length=30, blank=True)

if created:
    Profile.objects.create(user=instance)
instance.profile.save()

email = forms.EmailField(max_length=254, help_text='Required. Inform a valid email address.')

phone_number = forms.CharField(help_text='Required. Format: 03001234567')

idboard = forms.ModelChoiceField(queryset=Board_TB.objects.filter(pk__in=b[1,2]),required=False)

class Meta:

    model = User

    fields = ('username', 'email','password1', 'password2','phone_number','idboard')

if request.method == 'POST':

    form = SignUpForm(request.POST)

    if form.is_valid():

        user = form.save()

        user.refresh_from_db()  # load the profile instance created by the
signal

        user.profile.phone_number = form.cleaned_data.get('phone_number')
        user.profile.idboard = form.cleaned_data.get('idboard')
        user.save()

        raw_password = form.cleaned_data.get('password1')

        user = authenticate(username=user.username, password=raw_password)
        login(request, user)

        return redirect('index')

else:

    form = SignUpForm()

return render(request, 'accounts/signup.html',{'form' : form,})

but I am facing this error:
IntegrityError at /accounts/signup/
('23000', "[23000] [Microsoft][SQL Server Native Client 11.0][SQL Server]Cannot insert the value NULL into column 'idboard', table 'edxlinkdb.dbo.accounts_profile'; column does not allow nulls. UPDATE fails. (515) (SQLExecDirectW); [23000] [Microsoft][SQL Server Native Client 11.0][SQL Server]The statement has been terminated. (3621)")