The Rabanan hold that a Nazir Tamei may start counting his Nezirus after he brings his Chatas even though he did not bring his Olah.
R. Yishmael Ben R. Yochanan Ben Berokah says that a Nazir Tamei may not count his thirty days of Nezirus until he brings his Asham.
If a Nezirah became Teme'ah and she separated Korbanos Tum'ah and then her husband annulled her Neder she brings the Chatas ha'Of but not the Olas ha'Of. (1)
R. Yishmael holds that when a husband annuls the Neder of his wife the Neder is Batel retroactively.
R. Eliezer ha'Kapar holds that a Nazir is a sinner because he afflicts himself from drinking wine. (2)
According to R. Eliezer ha'Kapar someone who afflicts himself from all foods is certainly a sinner. (3)
If someone takes on Nezirus in a cemetery as soon as he becomes Tahor he may start his Nezirus Taharah.
R. Eliezer holds that a person who takes on Nezirus while he is Tamei if after he is Metaher he becomes Tamei on the first day, he does not bring the Korbanos Tum'ah.
If a Nazir Tahor becomes Tamei on the first day or last day of his Nezirus he does not have to recount his Nezirus.
R. Eliezer holds that a person who took on Nezirus while Tamei only brings Korbanos Tum'ah if he became Tamei on the second day of his Nezirus Taharah.
R. Eliezer holds that if someone says that he will be a Nazir for 100 days and he became Tamei on the first day he does not have to recount that day. (4)
If a Nazir becomes Tamei on his last day of Nezirus he does not have to recount his Nezirus.
Beis Shamai holds that if someone took on Nezirus in Chutz la'Aretz when he comes to Eretz Yisrael to bring his Korbanos he must keep another thirty days of Nezirus.
Beis Hillel holds that when he comes to Eretz Yisrael he must recount his entire Nezirus.
A BIT MORE
1. This is in accordance with R. Yishmael Ben R. Yochanan Ben Berokah who holds that an Olas Nazir Tamei is not a Doron and therefore it may not be brought. According to the Rabanan who hold that the Olah is a Doron it may be brought even though her husband annulled the Neder.
2. Even though the Pasuk only calls a Nazir Tamei a sinner that is because a Nazir Tamei accentuated his sin.
3. Such as a person who takes on a day of fasting.
4. When he becomes Tahor he only has to count 29 days.
R. Eliezer ha'Kapar holds that a Nazir is a sinner because he is afflicting himself from drinking wine. Why is it a sin to afflict oneself from wine? Rashi says in Maseches Ta'anis that it is not a Mitzvah to afflict oneself as our sages teach us that there is nothing wrong with Tzadikim to benefit from this world. Since there is no Mitzvah to afflict oneself if one does so it is for no reason and therefore it is a sin.
THE ANNULMENT OF NEZIRUS
If a Nezirah became Tamei and then her husband annulled her Neder she brings her Korbanos Tum'ah. (Rambam Hilchos Nezirus 9:11)