If you are willing to use another CAS system then PARI/GP can do the job:
> gp -q
? E = ellinit(ellfromeqn(-y^2 + x^3 + 23*x + 11));
? p = 257; x1 = 920547770587 + O(p^5); y1=sqrty1 = sqrt(x1^3 + 23*x1 + 11);
? ellisoncurve(E, s = [x1, y1])
1
? ellpow(E, s, 84) - s
[O(257^5), O(257^5)]
? x1
7 + 18*257 + 236*257^2 + 3*257^3 + 211*257^4 + O(257^5)
? y1
1 + 246*257 + 148*257^2 + 175*257^3 + 186*257^4 + O(257^5)
You can even use $\texttt{gp}$ from within Sage.